Sleep deprivation negatively affects fitness performance by impairing reaction time, reducing endurance, and decreasing muscle strength. Lack of sleep can also lead to diminished motivation and increased fatigue, making it challenging to maintain a consistent workout routine. Additionally, recovery periods are longer, which may hinder overall progress. Sleep plays an essential role in muscle repair and hormonal balance, so chronic sleep deprivation can lead to decreased performance and increased risk of injuries. Prioritizing quality sleep is crucial for achieving fitness goals.